Method of purifying oil



March 20, 1934. c. J. RODMAN ET AL 1,951,739

METHOD 0F PURIFYING OIL Filed July 9. 1950 2 Sheets-Sheet l Mai-ch 20, 1934.` c. J. RODMAN Er AL METHOD OF PUHIFYING OIL Filed July 9, 1930 2 Sheets-Sheet 2 *mmm INVENTORS Psi/mad' Mar. 2o, 1934 METHOD F PURIFYING OIL Clarence J. Rodman and Russell P. Dunmire,

Alliance, Ohio, assignors to The Buckeye Twist `lrhiil Company, Alliance, Ohio, a corporation of Application July 9, 1930, Serial No. 468,699

9 Claims.

This invention relates to a method of purifying oil, and more particularly to a method of purifying oil by means of which not only solids and free water are removed,.but in which the oil is rendered free from dissolved gases and moisture. The present invention constitutes an improvement' on the inventions disclosed in our patents, 1,824,498 patented September 22, 1931;

. 1,836,338 patented December l5, 193.1; 1,890,265

l0 patented December 6, 1932; and 1,919,669 patented `July 25, 1933. The invention is applicable to oils of -various types, but is particularly adapted for use in treating mineral hydrocarbon oils, especially those'used in electrical apparatus. In the purication of mineral hydrocarbon oils, our invention is applicable both to the preparation of new oils'and to the conditioning of oils which have been used in oil submerged electrical apparatus.

Mineral hydrocarbon oils are refined for and nd a wide application as an insulating medium in oil submerged electrical apparatus because of the dielectric strength characteristics of the oil. The oils are used both as a cooling and insulating medium in' transformers, voltage regulators and as an insulating medium in cable joints and the like. When hydrocarbon oils are used for these purposes, they are subjected to oxidation reactions resulting from the combined action of heat absorbed from the electrical apparatus, and the oxygen in thel atmosphere which has ready access to the oil. Complex hydrocarbons are chemically altered by such oxidation reactions resulting in the formation of organic acids, volatile hydrocarbons, soapl and deposits termed sludge. When hydrocarbon mineral oils are .used in electrical apparatus such as circuit breakers, the arcing action Which'takes place results in decomposition of the complex hydrocarbons forming elemental carbon, hydrogen, carbon monoxide, carbon dioxide, methane, and hydrocarbon vapors, all of which reduce the dielectric strength of the insulating medium. Concurrently with the decomposition of a portion of the oil, water may be formed due to the combination of hydrogen evolved in thev zone of the arc with oxygen dissolved in the oil. These traces of wa.- ter may be in true solution in the oil and together Withthe evolved carbon particles of colloidal size contribute to the deterioration of the insulating value of the oil.

Heretofora it has been attempted to remove water and suspensions by gravity, by centrifugal force, and by filtering. These processes, howthey failed to remove water oi true solution. volatile hydrocarbons and dissolved gases such as oxygen.

In accordance with the present invention, the oil to be puriiied is passed through a filter to partially remove solids and free water, is then pumped through a heater, and is sprayed at superatmospheric pressure into a chamber maintained under subatmospheric pressure. The heated oil is sprayed under superatmospheric pressure in order to subject the oil to a sudden shock which releases the dissolved gases and moisture from the sprayed particles. The volatiles are removed from the vacuum chamber, but the particles of oil are collected by bailles and caused to flow in a tortuous path while exposed to the reduced pressure toward the bottom of the chamber. From the bottom of the chamber the degasied oil is passed through a heat exchanger counter-current to the flow of incoming con-` taminated oil and is then ltered to remove the remaining solids and soluble sludges precipitable at low temperature. The passage of the degasined and dehydrated oil from the vacuum chamber through the heat exchanger not only results in economy due to heating the incoming oil, but also cools the degasiiied oilto substantially the temperature of the oil in the storage tank or other receptacle to which the oil is delivered after filtering. The lowering of the temperature of the oil by reason of the transfer of heat therefrom to the incoming oil in the heat exchanger also enables the oil to be filtered more effectively, as well as decreases the tendency of the oil in the storage tank to sweat and thereby reabsorb moisture.

In the accompanying drawings which illustrate the presentpreferredembodiment of our invention, 1

Figure 1 isa diagrammatic illustration of the oil purifying system, Y

Figure 2 is a vertical section through 'a lter used for partially removing solids and free water from contaminated oil,

Figure 3 is a detail perspective illustrating the construction of the filter discs, separators and cleaners employed in the lter shown in Figure 2, the parts being spaced apart for clearness,

Figure 4 is a detail perspective view of the discs, spacers` and cleaners in assembled position, and

Figure 5 is a sectional view of a spray nozzle used for spraying oil into'the vacuum chamber.

The oil to be puried generally contains solids, free water, dissolved water and dissolved gases. This contaminated oil is delivered through a the outlet opening 21.

pipe 2 provided with a ow indicatori! to a lter indicated generally by the reference numeral 4. The detailedconstruction oi the iilter is shown in Figures 2, 3 and 4. It consists essentially of a stack of round thin discs 5 provided with perforationsy 6, thru which the ltered liquid passes, spacers 7 disposed between adjacent ltering discs 5, and cleaners 8. The iilter discs, spacers and cleaners are illustrated in Figure 3 as spaced apart, while in Figure 4 these elements are shown in their assembled position. A hexagonal post 9 rits into corresponding openings 10 in the discs and spacers, and the post is provided with a handle 11, by means of which the discs and spacers may be rotated as a unit.

The discs and spacers are maintained in assembled position by a top washer 12 and a bottom washer 13, the washers having a screw 14 extending therethrough. Thel discs and spacers are assembled and the nut 15 is tightened to maintain the parts in assembled position. Between each of the discs 5, and opposite each o1' the spacers 7, is a cleaner 8. Each of the cleaners has a hexagonal opening 18, into which fits av hexagonal post 19. This post is non-rotatable and accordingly maintains the cleaners in fixed position.

The oil to be ltered flows in through the inlet opening 20 and passes between the edges of the discs 5 and then through the openings 6 in the discs flowing downwardly, and is delivered from The thickness of the spacers 7 determines the 'neness of the ltering operation. The solids which collect at the exposed edges of the discs are removed by turning the handle 11, which rotates the stack of discs and spacers relative to the stationary cleaners 8. The solid material flows downwardly through a passage 22 controlled by a valve 23 into a sump 24 from which it may be removed by opening the cover 25. A drain opening 26 and plug 27 are also provided in the sump. The material in the sump may be cleaned out without stopping the operation of the lter, if the valve 23 is rst turned to closed position.

The ltered oil is pumped by a pump 30 through conduits 31 and 32 to a heat exchanger indicated generally by the reference numeral 33. The pump is provided with a by-pass connection 34 controlled by a valve 35, in order to prevent excessive pressure on the pump. If the pressure tends to become too great, such as might be the case, for example, if the filter press, hereafter more fully described, should become clogged, the oil flows from ythe outlet side 36 of the pump through the by-pass 34, and returns to the inlet side 37 of the pump.

In the normal operation of the apparatus, the oil flows through conduit 32 controlled by a threeway valve 39 into the iirst unit 40 of the heat exchanger 33. The oil flows through the unit 40 on the outside of a conduit 41, then through a second three-way valve 42 and conduit 43 into a second heat exchange unit 44. It then flows through conduit 45, heat exchanger unit 46, conduit 47, heat exchanger unit 48 and conduit 49, into a heater 50. During the normal operation of the apparatus, the three-way valves 39 and 42 are disposed so that their passages are in the positions indicated by full lines in Figure l.

The heater 50 has a heating coil 51 which is connected by electrical conduits 52 to an automatic temperature control switch 53. The automatic temperature control switch 53 operates in accordance with the temperature of the oil in the'conduit 64, through which the oil ows on its way from the heater 50 to a vacuum tank 55. The particular construction of the temperature control switch 53 and the electrical circuits connecting it to a source of electrical energy are described and claimed-in our copending patent. 1,890,265. 'I'he particular construction of the switch and electrical connections are shown only in a diagrammatic manner in this application, since the construction is not here claimed. The arrangement of the switch and electrical connections is such, however, that the temperature of the oil owing through the conduit 54 prior to being delivered to the vacuum chamber 55 is automatically maintained at the desired temperature. This temperature is indicated by a thermometer 56.

The oil iiowng through conduit 54 is delivered to a spray nozzle indicated generally by the reference numeral 57 and by means of which it is broken up into a ne spray. The spray nozzle comprises a holder 58 which is connected by a pipe 59 to the conduit 54. Screwed into the holder 58 are several individual nozzles 60 constructed as shown in detail in Figure 5. The nozzle has a stem 61, the lower end of which is screwed into the holder 58. A cap 62 provided with a spray opening 63 is screwed onto the upper end 64 of the stem. The cap 62 has a plug 65 threaded therein, the plug being provided with two openj ings 66 extending therethrough. The plug 65 is conveniently screwed into the cap 62 by providing the plug with a groove 67, so that the plug may be turned by a screw-driver. The oil :dows through the stem 61 and then through the passages 66 into a chamber 68 from which it is delivered through the opening 63. In this manner the oil is sprayed upwardly in the vacuum tank and the particles of oil impinge against and are intercepted by aseries of battles indicated generally by the reference numeral 70. The oil is sprayed into the vacuum chamber under superatmospheric pressure, so that when the particles are released in the vacuum chamber, they are subjected to a sudden shock or impact which liberates the dissolved gases and moisture from the oil particles.

The baiiles 70 are of general trough shape and, as shown in the drawings, there are three series 71, 72 and 73 of the baiiles. The series of baiiies 111 :ll i

72 are disposed in staggered relation to the series of bailies 71 and 73. The baffles in the series 71 and 73 are disposed with their apexes extending upwardly while the baiiies in the series 72 have ther apexes extending downwardly.

The gases liberated in the vacuum chamber 55 flow upwardly in tortuous paths between the baiiie 70, and are delivered through a conduit 75 to a vacuum pump 76. The gases flow from the vacuum pump through a conduit 77 into a sepi tom of the separator. The bottom 81 of the separator slopes downwardly and outwardly from its center, thereby acting to collect the oil which is returned by the baiiies. The oil collected at the bottom of the separator is returned to the vacuum pump 76 through a pipe 82. 'Ihe bottom of the separator is provided with a drain pipe 83, by means of which any water collected at the bottom of the separator may be removed. The pipe 82 extends upwardly into the separator for a short distance, so that it acts to return oil only and not any water which may have collected in the bottom of the separator.

The oil sprayed from the nozzle 57 in the vacuum chamber is prevented from owing out of the top of the chamber by the baiiles '70. The oil particles collect in the trough shaped bales 70, from which they flow downwardly in tortuous paths while exposed to the vacuum in the chamber- 55. The tortuous flow of the oil streams is caused by bailles 90 arranged as indicated in Fgure 1 adjacent the side of the vacuum chamber and supported by frames 91 and 92. During the downward tortuous passage of the films of oil over the baffles 90, a further amount of volatiles are liberated from the oil and the volatiles escape from the top of the vacuum chamber through the conduit '75.

The particular temperature pressure and degree of vacuum used in the process varies according to the type of oil which is being treated. In treating transformer oil, we have found that before spraying it in the vacuum chamber it should be heated to a temperature of from 90 to 160 F., preferably from 140 to 160 F. The optimum temperature generally is about 150 F. The pressure to which the oil is raised before being sprayed from the nozzle 57 may vary between sixty and two hundred pounds per square inch, a pressure of one hundred to one hundred and fty pounds per square inch being the usual range which is employed. A pressure of about one hundred and twenty-five pounds per square inch is generally preferred for treating transformer oils under most circumstances. 'I'he vacuum in the vacuum chamber 55 should be maintained equivalent to from 28 to 30 inches of mercury, as referred to a 30 inch barometer. The best results have been obtained by employing a vacuum of between 29.5 to 29.7 inches of mercury.

The degasified oil collected in the bottom of the vacuum chamber 55 is forced by an oil pump 95 through conduit 41, which passes through the units 48, 46, 44 and 40 of the heat exchanger 33. The hot oil entering the unit 48 is cooled by its passage through the heat exchanger to a temperature such'that it may be effectively filtered in a lter press 100, to which the oil is delivered from the heat exchanger. The oil passing through the conduit 41 in the heat exchanger also raises the temperature of the incoming contaminated oil which surrounds it in the units 40, 44, 46 and 48. The passage of the degasified heated oil from the vacuum chamber 55 through the heat exchanger 33 accomplishes several very desirableresults. It is economical because it raises the temperature of the incoming oil so that less heat is required to be furnished by the heater 50, in order to raise the temperature of the oil to the desired degree before spraying it in the vacuum chamber.

The transfer of heat from the degasied oil to the incoming oil cools the degasified oil to such an extent that any remaining solids may beefiiciently removed in the subsequent filtering operation. In some cases there are soluble sludges present in the degasied oil which cannot be iiltered effectively unless the temperature of the oil is below about F. In such cases it is preferred to cool the degasified oil to about this temperature so that it may be effectively filtered. We prefer to cool the degasied oil to substantially the ambient temperature of the oil in the storage tank or other receptacle to which it is delivered after filtering. 'I'his equalization of the temperature of the degasiled oil prevents sweating or breathing of the tank which would tend to cause the formation of water, and thereby result in reabsorption of the water by the oil. If absorption were to take place it would, of course, decrease the insulating properties of the oil.

The portion of the conduit 41 between the filter press 100 and the heat exchanger unit 40 is provided with a thermometer 101 and also wlth a pressure limit switch indicated generally by the reference numeral 102. If the blotters in the iilter 100 tend to become clogged with solids, the pressure in the conduit 41 will be increased. 'I'he pressure limit switch 102 is employed for the purpose of preventing the building up of excessive pressures which might break the blotters in the lter press. The construction and electrical connections for the pressure limit switch 102 are shown and described in our copending patent, 1,890,265, previously referred to.

If the blotters of the illter press tend to clog, it raises the pressure in the conduit 4l. a diaphragm 103 against the action of a spring 104. 'Ihe diaphragm has an arm 105 connected thereto at one end. The arm is pivoted intermediate its ends as indicated at 106, and the upper end 107 of the arm is disposed so as to close and open the electric circuit of which the wires 108 form a part. 'I'he circuit including the leads 108 controls a switch `(not shown), which shuts oif the current from the motors for the pumps 30, 76 and 95, and also shuts off the current supplied to the heating coil 51 in the oil heater 50. Accordingly, ifthe pressure in the conduit 41 raises above the limit at which the pressure limit switch 102 is set, the switch is operable to stop the operation of the pumps 30, 76 and 95 and also to break the electrical connection for the heating element 51. y

The' cooled o il from the heat exchanger 33 flows through the filter press 100, wherein any solids which may have been precipitated due to cooling the oil are separated from the oil, and the puriiied oil is delivered through an outlet conduit 110 to a storage tank or directly to an electrical apparatus.

Under certain conditions it is desirable to cool the oil flowing through the conduit 41 to a greater degree than can be accomplished by simply transmitting heat from the oil in the conduit 41 to the oil which surrounds it in the heat exchanger elements 40, 44, 46 and 48. Accordingly we have provided a by-pass connection by means of which we can by-pass the contaminated oil around the unit 40 of the heat exchanger, and have provided means for additionally cooling the oil by using water as the cooling medium in this unit. This is accomplished by turning the three-way valves 39 and 42 so that their passages lare disposed in the ldotted line positions indicated in Figure 1, and by opening the valve 115, which in the normal practice is maintained closed. With the valves disposed in the dotted line positions and the valve 115 open, the contaminated oil is forced by the pump 30 through conduit 32, valve 115, conduits 111 and 43 to the heat exchanger unit 44. From the unit 44 the o il flows as previously described. The heat exchanger unit 40 is supplied with water which flows from a suitable source through conduit 112 and valve 39 into the unit 40.

This raises The water surrounds the oil contained in the conduit 41, thereby cooling it and the water then flows out of the unit through conduits 1713 and 114. This enables us to give an additional cooling effect to the oil in the conduit 41 if such oil is not cooled to the desired temperature by the simple transmission of heat therefrom to the incoming contaminated oil which surrounds it in the units of the heat exchanger 33.

The treatment of the oil in the vacuum chamber 55 as herein described eliminates substantially all dissolved gases and moisture. This treatment of the oil in the vacuum chamber combined with the cooling thereof in the heat exchanger enables the oil to be very eiciently filtered. Since the water has been substantially removed, soap sludges cannot be formed. These sludges may be formed if the oil is not substantially completely dehydrated. They tend to clog the blotters of the filter press, cause the building up of excessive pressures, and prevent the proper filtering of the oil. According to our method the precipitate resulting from cooling the degasiiied and dehydrated oil is in the nature of a loose granular precipitate which actually aids the filtering of the oil due to its deposition on the blotter papers to form an additional filtering surface.

We have illustrated and described a present preferred embodiment of our invention and have described the present preferred method of carrying out the process and have indicated certain preferred temperatures. It is to be understood, however. that the invention may be otherwise embodied or practiced within the scope of the following claims.

We claim:

l. The method of purifying oil which has been used in electrical apparatus, comprising heating the oil, spraying it under super-atmospheric pressure into a chamber maintained at subatmospheric pressure to release gases and moisture, collecting the degasiiied oil, cooling it to below about F. by transferring heat therefrom to incoming oil to precipitate solid sludges, and thereafter filtering the cooled oil.

2. The method of purifying oil which has been used in electrical apparatus, comprising heating the oil, spraying it under super-atmospheric pressure into a chamber maintained at subatmospheric pressure to release gases and moisture, collecting the degasified oil, cooling the degasiiied oil to a temperature sufiicient to precipitate soluble sludges by transferring heat therefrom to incoming oil, and thereafter filtering the cooled oil.

3. The method of purifying oil which has been used in electrical apparatus, comprising heating contaminated oil by heat exchange with degasified oil, spraying it under superatmospheric pressure into a chamber maintained at subatmospheric pressure to release gases and moisture, collecting the degasifled oil, cooling it by countercurrent heat exchange with contaminated oil to cool the degasified oil to a temperature suicient to precipitate soluble sludges, and thereafter filtering the cooled degasified oil.

4. The method of purifying oil which has been used in electrical apparatus, comprising heating the oil, spraying it under super-atmospheric pressure into a chamber maintained at subatmospheric pressure to release gases and moisture, collecting the degasifled oil, cooling it to below 85 F. and to about the ambient temperature of the container to which the oil is to be delivered lafter filtering, and then filtering the oil.

5. The method of purifying oil, comprising heating the oil, spraying it under super-atmospheric pressure into a chamber maintained at subatmospheric pressure to release gases and moisture, collecting the degasiiied oil, cooling the degasified oil by transferring heat therefrom to incoming contaminated oil to a temperature sufficient to precipitate dissolved sludges, and thereafter filtering the oil to remove the precipitated sludges.

6. The method of purifying oil which has been used in electrical apparatus, comprising filtering the impure oil to partially remove solids and free water, heating the oil, spraying it under superatmospheric pressure into a chamber maintained at subatmospheric pressure to release gases and moisture, collecting the degasiiied oil, cooling the degasiiied oil to a temperature suiiicient to precipitate soluble sludges by transferring heat therefrom to incoming impure oil, and thereafter filtering the cooled oil to separate the precipitate.

7. The method of purifying oil for electrical insulation purposes, comprising heating the oil, spraying it under pressure of at least 60 pounds per square inch into a vacuum chamber maintained under a vacuum of from 28 to 30 inches of mercury as referred to a 30 inch barometer, collecting the degasifled oil, cooling it by transferring heat therefrom to incoming contaminated oil, and filtering the cooled oil.

8. The method of purifying oil for electrical insulation purposes, comprising heating it to a temperature of between 90 and 160 F., spraying it under pressure of between 60 and 200 pounds per square inch into a vacuum chamber maintained under a vacuum of from 28 to 30 inches of mercury as referred to a 30 inch barometer, collecting the degasified oil, cooling it by transferring heat therefrom to incoming oil, and filtering the cooled oil.

9. The method of purifying oil for electrical insulation purposes, comprising heating it to a temperature of about 15.0 F., spraying it under pressure of about 125 pounds per square inch into a vacuum chamber maintained under a 'vacuum of from 29.5 to 29.7 inches of mercury as referred to a 30 inch barometer, collecting the degasified oil, cooling it by transferring heat therefrom to incoming oil, and filtering the cooled oil.

CLARENCE J. RODMAN. RUSSELL P. DUNMIRE.

CERTIFICATE 0l"v CCRREC'IION.

Patent No. 1,951,739. l' March 20, 1934.

CLARENCE J. RODMAIjI, ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, line 87, claim 5-, after "oil" insert the words which has been used in electrical apparatus; and tha-t the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of May, A. D. 1934.

Bryan M. Battey (Seal) Acting Commissioner of Patents. 

